Semiconductor device with a metal gate stack having tapered sidewalls

ABSTRACT

A semiconductor device includes a metal gate stack. The metal gate stack includes a high-k gate dielectric and a metal gate electrode over the high-k gate dielectric. The metal gate electrode includes a first top surface and a second bottom surface substantially diametrically opposite the first top surface. The first top surface includes a first surface length and the second bottom surface includes a second surface length. The first surface length is larger than the second surface length. A method of forming a semiconductor device is provided.

RELATED APPLICATION

This application claims priority to and is a divisional of U.S. patent application Ser. No. 15/376,610, titled “SEMICONDUCTOR DEVICE WITH AN ANGLED SIDEWALL GATE STACK” and filed on Dec. 12, 2016, which claims priority to and is a divisional of U.S. patent application Ser. No. 14/024,848, titled “SEMICONDUCTOR DEVICE WITH AN ANGLED SIDEWALL GATE STACK” and filed on Sep. 12, 2013. U.S. patent application Ser. No. 15/376,610 and U.S. patent application Ser. No. 14/024,848 are incorporated herein by reference.

BACKGROUND

In a semiconductor device, current flows through a channel region between a source region and a drain region upon application of a sufficient voltage or bias to a gate of the device. When current flows through the channel region, the device is generally regarded as being in an ‘on’ state, and when current is not flowing through the channel region, the device is generally regarded as being in an ‘off’ state.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to be an extensive overview of the claimed subject matter, identify key factors or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

One or more techniques, and resulting structures, for forming a semiconductor device are provided herein.

The following description and annexed drawings set forth certain illustrative aspects and implementations. These are indicative of but a few of the various ways in which one or more aspects are employed. Other aspects, advantages, and/or novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the annexed drawings.

DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are understood from the following detailed description when read with the accompanying drawings. It will be appreciated that elements and/or structures of the drawings are not necessarily be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily increased and/or reduced for clarity of discussion.

FIG. 1 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 2 illustrates forming a gate dielectric associated with forming a semiconductor device, according to an embodiment;

FIG. 3 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 4 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 5 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 6 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 7 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 8 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 9 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 10 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 11 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 12 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 13 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 14 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 15 illustrates forming a gate electrode associated with forming a semiconductor device, according to an embodiment;

FIG. 16 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 17 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 18 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 19 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 20 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 21 illustrates a portion of a semiconductor device, according to an embodiment;

FIG. 22 illustrates forming a gate dielectric associated with forming a semiconductor device, according to an embodiment;

FIG. 23 illustrates forming a gate electrode associated with forming a semiconductor device, according to an embodiment;

FIG. 24 illustrates a method of forming a semiconductor device, according to an embodiment; and

FIG. 25 illustrates a method of forming a semiconductor device, according to an embodiment.

DETAILED DESCRIPTION

The claimed subject matter is now described with reference to the drawings, wherein like reference numerals are generally used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide an understanding of the claimed subject matter. It is evident, however, that the claimed subject matter may be practiced without these specific details. In other instances, structures and devices are illustrated in block diagram form in order to facilitate describing the claimed subject matter.

One or more techniques for forming a semiconductor device and resulting structures formed thereby are provided herein.

FIG. 1 is a sectional view illustrating a semiconductor device 100 according to some embodiments. In an embodiment, the semiconductor device 100 is formed upon a substrate 102. The substrate 102 comprises any number of materials, such as, for example, silicon, polysilicon, germanium, etc., alone or in combination. According to some embodiments, the substrate 102 comprises an epitaxial layer, a silicon-on-insulator (SOI) structure, etc. According to some embodiments, the substrate 102 corresponds to a wafer or a die formed from a wafer.

According to some embodiments, an interfacial layer 104 is formed over the substrate 102. The interfacial layer 104 includes any number of materials, including oxides, silicon oxide, etc. In some embodiments, an interfacial layer thickness 106 of the interfacial layer 104 is between about 5 angstroms to about 20 angstroms. The interfacial layer 104 is formed in any number of ways, such as by atomic layer deposition (ALD), chemical vapor deposition (CVD), other suitable processes, etc.

Turning to FIG. 2, a gate dielectric 200 is formed over the interfacial layer 104. The gate dielectric 200 comprises any number of materials, including, for example, oxides, silicon dioxide, Al₂O₃, HfO, HfO₂, ZrO, ZrO₂, ZrSiO, YO, Y₂O₃, LaO, La₂O₅, GdO, Gd₂O₅, TiO, TiO₂, TiSiO, TaO, Ta₂O₅, TaSiO, HfErO, HfLaO, HfYO, HfGdO, HfAlO, HfZrO, HfTiO, HfTaO, HfSiO, SrTiO, ZrSiON, HfZrTiO, HfZrSiON, HfZrLaO, HfZrAlO, or combinations thereof, etc., alone or in combination. In some embodiments, the gate dielectric comprises a high-k gate dielectric. In some embodiments, a gate dielectric thickness 202 of the gate dielectric 200 is between about 5 angstroms to about 30 angstroms. The gate dielectric 200 is formed in any number of ways, such as by deposition, chemical vapor deposition (CVD), or other suitable processes, for example.

Turning now to FIG. 3, a cap layer 300 is formed over the gate dielectric 200. The cap layer 300 comprises any number of materials, including, for example, gold, tin, silver, TiN, etc. In some embodiments, a cap layer thickness 302 of the cap layer 300 is between about 5 angstroms to about 30 angstroms. The cap layer 300 is formed in any number of ways, such as by deposition, chemical vapor deposition (CVD), or other suitable processes, for example. In some embodiments, the cap layer 300 is an etch stop layer.

Turning now to FIG. 4, in an embodiment, a dummy layer 400 is formed over the cap layer 300 and over the substrate 102. In some embodiments, the dummy layer 400 comprises silicon, polysilicon, other semiconductor materials, etc. The dummy layer 400 is formed in any number of ways, such as by deposition and patterning, for example. According to some embodiments, a dummy layer thickness 402 of the dummy layer 400 is between about 700 angstroms to about 900 angstroms.

Turning now to FIG. 5, in an embodiment, a mask region 500 is formed over the dummy layer 400. The mask region 500 includes any number of materials, including silicon oxide, silicon nitride, nitride, Si₃N₄, etc., alone or in combination. In some embodiments, the mask region 500 is patterned to form a first opening 502 and a second opening 504 on sides of the mask region 500.

In an embodiment, the mask region 500 comprises a first mask portion 510 formed over the dummy layer 400. The first mask portion 510 includes any number of materials, including SiN, in an embodiment. In some embodiments, a first mask thickness 512 of the first mask portion 510 is between about 50 angstroms to about 150 angstroms.

In an embodiment, the mask region 500 comprises a second mask portion 520 formed over the first mask portion 510. The second mask portion 520 includes any number of materials, including oxides, plasma enhanced oxygen (PEOX), etc., in an embodiment. In some embodiments, a second mask thickness 522 of the second mask portion 520 is between about 500 angstroms to about 600 angstroms.

Turning now to FIG. 6, in some embodiments, a bottom layer 600 is formed over the dummy layer 400 and mask region 500. In some embodiments, the bottom layer 600 includes a photoresist material. The bottom layer 600 is formed in any number of ways, such as by deposition, for example. In some embodiments, a bottom layer thickness 602 of the bottom layer 600 is between about 1500 angstroms to about 2500 angstroms.

In some embodiments, a bottom anti-reflective coating (BARC) layer 610 is formed over the bottom layer 600. The BARC layer 610 includes any number of materials, including silicon, other semiconductor materials, etc. In an embodiment, a BARC layer thickness 612 of the BARC layer 610 is between about 700 angstroms to about 900 angstroms.

In some embodiments, a photoresist layer 620 is formed over the BARC layer 610. The photoresist layer 620 includes any number of photoresist materials. In an embodiment, a photoresist layer thickness 622 of the photoresist layer 620 is between about 1000 angstroms to about 1200 angstroms.

Turning now to FIG. 7, in some embodiments, the photoresist layer 620 is removed, such as by wet etching, dry etching, etc. According to some embodiments, an etch chemistry for etching through the photoresist layer 620 includes Cl₂, O₂, H₂, Ch₄, CF₄, Ar, He, CHF₃, SF₆, etc., alone or in combination. In some embodiments, the etch chemistry for etching through the photoresist layer 620 includes CHF₃ and SF₆ for a time period of between about 1 second to about 100 seconds at a temperature of about 60° Celsius.

Turning now to FIG. 8, in some embodiments, the BARC layer 610 is removed, such as by wet etching, dry etching, etc. In some embodiments, the BARC layer 610 is removed after etching through the photoresist layer 620. According to some embodiments, an etch chemistry for etching through the BARC layer 610 includes CF₄, CHF₃, CH₂F₂, SF₆, O₂, N₂, Ar, He, Cl₂, etc., alone or in combination. In some embodiments, an etching time for etching through the BARC layer 610 is between about 1 second to about 100 seconds. In some embodiments, an etch pressure for etching through the BARC layer 610 is between about 1 millitorr (mTorr) to about 30 mTorr. In some embodiments, a source wattage for etching through the BARC layer 610 is between about 100 watts to about 2000 watts. In some embodiments, a bias wattage for etching through the BARC layer 610 is between about 0 watts to about 800 watts.

Turning now to FIG. 9, in some embodiments, the bottom layer 600 is removed, such as by wet etching, dry etching, etc. In some embodiments, the bottom layer 600 is removed after etching through the BARC layer 610. According to some embodiments, an etch chemistry for etching through the bottom layer 600 includes CF₄, CHF₃, CH₂F₂, SO₂, Ar, He, N₂, Cl₂, etc., alone or in combination. In some embodiments, an etching time for etching through the bottom layer 600 is between about 1 second to about 200 seconds. In some embodiments, an etch pressure for etching through the bottom layer 600 is between about 1 millitorr (mTorr) to about 30 mTorr. In some embodiments, a source wattage for etching through the bottom layer 600 is between about 100 watts to about 2000 watts. In some embodiments, a bias wattage for etching through the bottom layer 600 is between about 0 watts to about 800 watts.

Turning now to FIG. 10, in some embodiments, the dummy layer 400 is etched as part of a first dummy layer etching 1000. According to some embodiments, an etch chemistry for etching the dummy layer 400 during the first dummy layer etching 1000 includes CL₂, CF₄, etc., alone or in combination. In some embodiments, a gas ratio of CL₂ to CF₄ is about 10 standard cubic centimeters per minute (SCCM) to about 50 SCCM of CL₂ to about 100 SCCM to about 150 SCCM of CF₄. In some embodiments, an etching time for the first dummy layer etching 1000 is between about 0 seconds to about 50 seconds. In some embodiments, an etch temperature during the first dummy layer etching 1000 is between about 15° Celsius to about 50° Celsius. In some embodiments, the first dummy layer etching 1000 comprises etching through a first depth 1002 of the dummy layer 400 that is between about 400 angstroms to about 600 angstroms.

Turning now to FIG. 11, in some embodiments, the dummy layer 400 is etched as part of a second dummy layer etching 1100. According to some embodiments, an etch chemistry for etching the dummy layer 400 during the second dummy layer etching 1100 includes CL₂, CF₄, etc., alone or in combination. In some embodiments, a gas ratio of CL₂ to CF₄ is about 25 SCCM to about 35 SCCM of CL₂ to about 125 SCCM to about 135 SCCM of CF₄. In some embodiments, an etching time for the second dummy layer etching 1100 is between about 5 seconds to about 50 seconds. In some embodiments, an etch temperature during the second dummy layer etching 1100 is between about 15° Celsius to about 50° Celsius. In some embodiments, the second dummy layer etching 1100 comprises etching through a second depth 1102 (illustrated in FIG. 10) of the dummy layer 400 that is between about 100 angstroms to about 200 angstroms.

Turning now to FIG. 12, in some embodiments, the dummy layer 400, cap layer 300, gate dielectric 200, and interfacial layer 104 are etched as part of a third dummy layer etching 1200. According to some embodiments, an etch chemistry for etching an unetched portion 1220 (illustrated in FIG. 11) of the dummy layer 400 during the third dummy layer etching 1200 includes CL₂, CF₄, CHF₃, HBr, N₂, Ar, He, etc., alone or in combination. In some embodiments, a gas ratio of CL₂ to CF₄ to CHF₃ is about 25 SCCM to about 35 SCCM of CL₂ to about 60 SCCM to about 80 SCCM of CF₄ to about 10 SCCM to about 30 SCCM of CHF₃. In some embodiments, an etching time for the third dummy layer etching 1200 is between about 5 seconds to about 50 seconds. In some embodiments, the third dummy layer etching 1200 comprises etching sidewalls 1210 of the dummy layer 400. In some embodiments, the third dummy layer etching 1200 comprises etching through a third depth 1202 (illustrated in FIG. 11) of the dummy layer 400 that is between about 40 angstroms to about 60 angstroms.

In certain embodiments, increasing the gas flow of CL₂ in the etching gases for the first dummy layer etching 1000, the second dummy layer etching 1100, or the third dummy layer etching 1200 forms a re-entrant profile for the dummy layer 400 with a sidewall angle that is less than about 90 degrees with respect to the substrate 102.

In some embodiments, the third dummy layer etching 1200 comprises etching through the cap layer 300, gate dielectric 200, and interfacial layer 104. In some embodiments, the third dummy layer etching 1200 for etching through the cap layer 300, gate dielectric 200, and interfacial layer 104 includes the same etch chemistry and properties as the third dummy layer etching 1200. In some embodiments, the third dummy layer etching 1200 for etching through the cap layer 300, gate dielectric 200, and interfacial layer 104 includes a different etch chemistry and properties than for etching through the dummy layer 400. In an embodiment, the etch chemistry for etching through the cap layer 300, gate dielectric 200, and interfacial layer 104 includes BCL₃, CL₂, O₂, N₂, Ar, etc., alone or in combination. In some embodiments, an etching time for etching through the cap layer 300, gate dielectric 200, and interfacial layer 104 is between about 5 seconds to about 50 seconds. According to some embodiments, the third dummy layer etching 1200 comprises patterning sidewalls 1280 of the cap layer 300, gate dielectric 200, and interfacial layer 104, such that the sidewalls 1280 form an angle that is not equal to 90 degrees with respect to the substrate 102. Accordingly, in some embodiments, the forming the gate dielectric 200 comprises patterning the sidewalls 1280. As such, in some embodiments, the photoresist layer 620 (illustrated in FIG. 6) is etched before the gate dielectric 200 is formed.

Turning now to FIG. 13, in an embodiment, one or more spacers 1300 are formed surrounding at least one of the dummy layer 400, cap layer 300, gate dielectric 200, or interfacial layer 104. In some embodiments, the one or more spacers 1300 comprises a first spacer portion 1302 and a second spacer portion 1304. In some embodiments, the first spacer portion 1302 of the spacer 1300 is formed on a first side 1310 of the dummy layer 400, cap layer 300, gate dielectric 200, and interfacial layer 104 while the second spacer portion 1304 of the spacer 1300 is formed on a second side 1312. The first spacer portion 1302 and second spacer portion 1304 comprise any number of dielectric materials, such as nitrides, oxides, etc., alone or in combination. The first spacer portion 1302 and second spacer portion 1304 are formed in any number of ways, such as by thermal growth, chemical growth, atomic layer deposition (ALD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or other suitable techniques, for example. In some embodiments, the first spacer portion 1302 and second spacer portion 1304 are etched, such that a top surface 1320 of the first spacer portion 1302 and second spacer portion 1304 is generally planar with respect to a top surface 1340 of the dummy layer 400.

In some embodiments, the top surface 1340 of the dummy layer 400 is substantially diametrically opposite a bottom surface 1370 of the dummy layer 400. According to some embodiments, the top surface 1340 of the dummy layer 400 is substantially parallel to the bottom surface 1370 of the dummy layer 400. In certain embodiments, a top surface length 1372 of the top surface 1340 is not equal to a bottom surface length 1374 of the bottom surface 1370. In some embodiment, the top surface length 1372 of the top surface 1340 is larger than the bottom surface length 1374 of the bottom surface 1370.

Turning now to FIG. 14, the dummy layer 400, first mask portion 510, and second mask portion 520 are removed, such as by etching. According to some embodiments, an etch chemistry for etching the dummy layer 400, first mask portion 510, and second mask portion 520 includes CF₄, CHF₃, Cl₂, etc., alone or in combination. In some embodiments, an etching time for etching the dummy layer 400, first mask portion 510, and second mask portion 520 is between about 0 seconds to about 50 seconds. In some embodiments, after the dummy layer 400 is removed, an opening 1400 is formed between the first spacer portion 1302 and second spacer portion 1304, and a top surface 1402 of the cap layer 300 is exposed.

In some embodiments, the opening 1400 is defined between the first spacer portion 1302 and second spacer portion 1304 of the spacers 1300. In some embodiments, a top opening length 1450 of the opening 1400 is not equal to a bottom opening length 1452 of the opening 1400. In certain embodiments, the top opening length 1450 of the opening 1400 is larger than the bottom opening length 1452 of the opening 1400.

Turning now to FIG. 15, according to some embodiments, a gate electrode 1500 is formed within the opening 1400 (illustrated in FIG. 14) between the first spacer portion 1302 and second spacer portion 1304 and over the cap layer 300. The gate electrode 1500 is formed in any number of ways, such as by deposition, epitaxial growth, etc., for example. In some embodiments, the gate electrode 1500 includes a conductive material, such as aluminum, copper, etc., alone or in combination. In some embodiments, the gate electrode 1500 comprises a metal gate electrode. In some embodiments, a gate stack 1502 comprises the gate electrode 1500, cap layer 300, gate dielectric 200, and interfacial layer 104, with the gate electrode 1500 over the gate dielectric 200. In some embodiments, the gate stack 1502 comprises a metal gate stack.

In some embodiments, the gate electrode 1500 comprises a first top surface 1510 and a second bottom surface 1512 that is substantially diametrically opposite the first top surface 1510. In some embodiments, the first top surface 1510 is parallel to the second bottom surface 1512. In some embodiments, the second bottom surface 1512 is in closer proximity to the gate dielectric 200 than the first top surface 1510 is to the gate dielectric 200. In some embodiments, the first top surface 1510 comprises a first surface length 1520 and the second bottom surface 1512 comprises a second surface length 1522. In some embodiments, the first surface length 1520 is not equal to the second surface length 1522. In some embodiments, the first surface length 1520 is larger than the second bottom surface length 1522.

In some embodiments, the gate electrode 1500 comprises a third surface 1530 and a fourth surface 1532 that is substantially diametrically opposite the third surface 1530. According to some embodiments, the third surface 1530 is not parallel with respect to the fourth surface 1532.

According to some embodiments, the second bottom surface 1512 is at a first angle 1540 with respect to the third surface 1530. In some embodiments, the first angle 1540 is greater than about 90 degrees. In some embodiments, the second bottom surface 1512 is at a second angle 1542 with respect to the fourth surface 1532. In some embodiments, the second angle 1542 is greater than about 90 degrees. In an embodiment, the first angle 1540 is substantially equal to the second angle 1542.

According to some embodiments, the first top surface 1510 is at a third angle 1550 with respect to the third surface 1530. In some embodiments, the third angle 1550 is less than about 90 degrees. According to some embodiments, the first top surface 1510 is at a fourth angle 1552 with respect to the fourth surface 1532. In some embodiments, the fourth angle 1552 is less than about 90 degrees. In an embodiment, the third angle 1550 is substantially equal to the fourth angle 1552.

In some embodiments, the gate stack 1502 comprises a first sidewall 1560. In an embodiment, the first sidewall 1560 is adjacent to the second spacer portion 1304. In some embodiments, the first sidewall 1560 comprises the third surface 1530 of the gate electrode 1500 and a first surface 1564 of the cap layer 300, gate dielectric 200, and interfacial layer 104. According to some embodiments, the first sidewall 1560 is at a first sidewall angle 1562 with respect to a surface 1590 of the substrate 102 over which the semiconductor device 100 is formed. In some embodiments, the first sidewall angle 1562 is not equal to 90 degrees. In some embodiments, the first sidewall angle 1562 is less than 90 degrees.

In some embodiments, the gate stack 1502 comprises a second sidewall 1570 that is substantially diametrically opposite the first sidewall 1560. In an embodiment, the second sidewall 1570 is adjacent to the first spacer portion 1302. In some embodiments, the second sidewall 1570 is comprises the fourth surface 1532 of the gate electrode 1500 and a second surface 1574 of the cap layer 300, gate dielectric 200, and interfacial layer 104. According to some embodiments, the second sidewall 1570 is at a second sidewall angle 1572 with respect to the surface 1590 of the substrate 102. In some embodiments, the second sidewall angle 1572 is not equal to 90 degrees. In some embodiments, the second sidewall angle 1572 is less than 90 degrees.

FIG. 16 illustrates a second example semiconductor device 1600. According to some embodiments, the second semiconductor device 1600 comprises the dummy layer 400 formed over the substrate 102. According to some embodiments, the second semiconductor device 1600 comprises the mask region 500, first mask portion 510, second mask portion 520, etc.

In some embodiments, the second semiconductor device 1600 comprises the bottom layer 600, BARC layer 610, and photoresist layer 620 (illustrated in FIGS. 6 to 9). As described with respect to FIG. 6, in some embodiments, the bottom layer 600 is formed over the dummy layer 400, the BARC layer 610 is formed over the bottom layer 600, and the photoresist layer 620 is formed over the BARC layer 610. As described with respect to FIGS. 7 to 9, the bottom layer 600, BARC layer 610, and photoresist layer 620 are removed from the dummy layer 400, such as by etching.

Turning now to FIG. 17, in some embodiments, the dummy layer 400 is etched as part of the first dummy layer etching 1000. In some embodiments, the first dummy layer etching 1000 comprises etching through the first depth 1002 of the dummy layer 400. In FIG. 18, according to some embodiments, the dummy layer 400 is etched as part of the second dummy layer etching 1100. According to some embodiments, the second dummy layer etching 1100 comprises etching through the second depth 1102 (illustrated in FIG. 17).

Turning to FIG. 19, in some embodiments, the dummy layer 400 is etched as part of the third dummy layer etching 1200. According to some embodiments, as a result of the third dummy layer etching 1200, the unetched portion 1220 of the dummy layer 400 (illustrated in FIG. 18) is removed and the sidewalls 1210 of the dummy layer 400 are etched.

In some embodiments, the top surface 1340 of the dummy layer 400 is substantially diametrically opposite the bottom surface 1370 of the dummy layer 400. According to some embodiments, the top surface 1340 of the dummy layer 400 is substantially parallel to the bottom surface 1370 of the dummy layer 400. In certain embodiments, the top surface length 1372 of the top surface 1340 is not equal to the bottom surface length 1374 of the bottom surface 1370. In some embodiment, the top surface length 1372 of the top surface 1340 is larger than the bottom surface length 1374 of the bottom surface 1370.

In FIG. 20, in an embodiment, the spacer 1300, comprising the first spacer portion 1302 and second spacer portion 1304, is formed surrounding the dummy layer 400. In some embodiments, the first spacer portion 1302 is formed on the first side 1310 of the dummy layer 400 while the second spacer portion 1304 is formed on the second side 1312. In FIG. 21, the dummy layer 400 is removed, such as by etching. In some embodiments, after the dummy layer 400 is removed, the opening 1400 is formed between the first spacer portion 1302 and second spacer portion 1304.

In some embodiments, the opening 1400 is defined between the first spacer portion 1302 and second spacer portion 1304 of the spacers 1300. In some embodiments, the top opening length 1450 of the opening 1400 is not equal to the bottom opening length 1452 of the opening 1400. In certain embodiments, the top opening length 1450 of the opening 1400 is larger than the bottom opening length 1452 of the opening 1400.

Turning to FIG. 22, according to some embodiments, the interfacial layer 104 is formed within the opening 1400. In some embodiments, the interfacial layer thickness 106 of the interfacial layer 104 is between about 5 angstroms to about 20 angstroms. According to some embodiments, the gate dielectric 200 is formed over the interfacial layer 104 and over the substrate 102. In an embodiment, the gate dielectric 200 is formed within the opening 1400 between the first spacer portion 1302 and the second spacer portion 1304 of the spacers 1300. In some embodiments, the gate dielectric thickness 202 of the gate dielectric 200 is between about 5 angstroms to about 30 angstroms. Although not illustrated in FIG. 3, according to some embodiments, the cap layer 300 is formed over the gate dielectric 200.

Turning now to FIG. 23, in an embodiment, the gate electrode 1500 is formed within the opening (illustrated in FIG. 22) between the first spacer portion 1302 and second spacer portion 1304 and over the gate dielectric 200. In some embodiments, the gate stack 1502 comprises the gate electrode 1500, gate dielectric 200, and interfacial layer 104.

In some embodiments, the gate electrode 1500 comprises the first top surface 1510 and the second bottom surface 1512 that is substantially diametrically opposite the first top surface 1510. In some embodiments, the first top surface 1510 is parallel to the second bottom surface 1512. In some embodiments, the second bottom surface 1512 is in closer proximity to the gate dielectric 200 than the first top surface 1510. In some embodiments, the first top surface 1510 comprises the first surface length 1520 and the second bottom surface 1512 comprises the second surface length 1522. In some embodiments, the first surface length 1520 is not equal to the second surface length 1522. In some embodiments, the first surface length 1520 is larger than the second surface length 1522.

In some embodiments, the gate electrode 1500 comprises the third surface 1530 and the fourth surface 1532 that is substantially diametrically opposite the third surface 1530. According to some embodiments, the third surface 1530 is not parallel with respect to the fourth surface 1532.

According to some embodiments, the second bottom surface 1512 is at the first angle 1540 with respect to the third surface 1530. In some embodiments, the first angle 1540 is greater than about 90 degrees. In some embodiments, the second bottom surface 1512 is at the second angle 1542 with respect to the fourth surface 1532. In some embodiments, the second angle 1542 is greater than about 90 degrees. In an embodiment, the first angle 1540 is substantially equal to the second angle 1542.

According to some embodiments, the first top surface 1510 is at the third angle 1550 with respect to the third surface 1530. In some embodiments, the third angle 1550 is less than about 90 degrees. According to some embodiments, the first top surface 1510 is at the fourth angle 1552 with respect to the fourth surface 1532. In some embodiments, the fourth angle 1552 is less than about 90 degrees. In an embodiment, the third angle 1550 is substantially equal to the fourth angle 1552.

In some embodiments, the gate stack 1502 comprises the first sidewall 1560. In an embodiment, the first sidewall 1560 is adjacent to the second spacer portion 1304. In some embodiments, the first sidewall 1560 comprises the third surface 1530 of the gate electrode 1500 and the first surface 1564 of the gate dielectric 200 and interfacial layer 104. According to some embodiments, the first sidewall 1560 is at the first sidewall angle 1562 with respect to the surface 1590 of the substrate 102 over which the semiconductor device 100 is formed. In some embodiments, the first sidewall angle 1562 is not equal to 90 degrees. In some embodiments, the first sidewall angle 1562 is less than 90 degrees.

In some embodiments, the gate stack 1502 comprises the second sidewall 1570 that is substantially diametrically opposite the first sidewall 1560. In an embodiment, the second sidewall 1570 is adjacent to the first spacer portion 1302. In some embodiments, the second sidewall 1570 is comprises the fourth surface 1532 of the gate electrode 1500 and the second surface 1574 of the gate dielectric 200 and interfacial layer 104. According to some embodiments, the second sidewall 1570 is at the second sidewall angle 1572 with respect to the surface 1590 of the substrate 102. In some embodiments, the second sidewall angle 1572 is not equal to 90 degrees. In some embodiments, the second sidewall angle 1572 is less than 90 degrees.

According to some embodiments, the semiconductor device 100, 1600 includes the gate electrode 1500 of the gate stack 1502 having the first top surface 1510 and the second bottom surface 1512. In some embodiments, the first surface length 1520 of the first top surface 1510 is not equal to the second surface length 1522 of the second bottom surface 1512. In some embodiments, due to the first surface length 1520 not being equal to the second surface length 1522, the semiconductor device 100, 1600 exhibits a reduced number of defects in the gate electrode 1500. Additionally, according to some embodiments, the semiconductor device 100, 1600 exhibits improved uniformity performance.

In an embodiment, a semiconductor device, such as semiconductor device 100, 1600, comprises a metal gate stack 1502 comprising a high-k gate dielectric 200 and a metal gate electrode 1500 over the high-k gate dielectric 200. In an embodiment, the metal gate electrode 1500 comprises a first top surface 1510 and a second bottom surface 1512 substantially diametrically opposite the first top surface 1510. In an embodiment, the first top surface 1510 comprises a first surface length 1520 and the second bottom surface 1512 comprises a second surface length 1522. In an embodiment, the first surface length 1520 is larger than the second surface length 1522.

An example method 2400 of forming a semiconductor device, such as semiconductor device 100, 1600, according to some embodiments, is illustrated in FIG. 24. At 2402, the gate dielectric 200 is formed. At 2404, a silicon dummy layer 400 is formed over the gate dielectric 200 such that a top surface 1340 of the silicon dummy layer 400 is substantially diametrically opposite a bottom surface 1370 of the silicon dummy layer 400, and such that a top surface length 1372 of the top surface 1340 is not equal to a bottom surface length 1374 of the bottom surface 1370. At 2406, the silicon dummy layer 400 is replaced with a metal gate electrode 1500.

An example method 2500 of forming a semiconductor device, such as semiconductor device 100, 1600, according to some embodiments, is illustrated in FIG. 25. At 2502, a silicon dummy layer 400 is formed over a substrate 102 such that a top surface 1340 of the silicon dummy layer 400 is substantially diametrically opposite a bottom surface 1370 of the silicon dummy layer 400, and such that a top surface length 1372 of the top surface 1340 is not equal to a bottom surface length 1374 of the bottom surface 1370. At 2504, spacers 1300 are formed on a first side 1310 and a second side 1312 of the silicon dummy layer 400. At 2506, the silicon dummy layer 400 is removed to define an opening 1400 between the spacers 1300 such that a top opening length 1450 of the opening 1400 is not equal to a bottom opening length 1452 of the opening 1400. At 2508, a gate dielectric 200 is formed within the opening 1400 between the spacers 1300 over the substrate 102. At 2510, a metal gate electrode 1500 is formed over the gate dielectric 200 between the spacers 1300 such that a first top surface 1510 of the metal gate electrode 1500 is substantially diametrically opposite a second bottom surface 1512 of the metal gate electrode 1500, and such that a first surface length 1520 of the first top surface 1510 is not equal to a second surface length 1522 of the second bottom surface 1512.

Although the subject matter has been described in language specific to structural features or methodological acts, it is to be understood that the subject matter of the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order in which some or all of the operations are described should not be construed to imply that these operations are necessarily order dependent. Alternative ordering will be appreciated having the benefit of this description. Further, it will be understood that not all operations are necessarily present in each embodiment provided herein. Also, it will be understood that not all operations are necessary in some embodiments.

It will be appreciated that layers, regions, features, elements, etc. depicted herein are illustrated with particular dimensions relative to one another, such as structural dimensions and/or orientations, for example, for purposes of simplicity and ease of understanding and that actual dimensions of the same differ substantially from that illustrated herein, in some embodiments. Additionally, a variety of techniques exist for forming the layers, regions, features, elements, etc. mentioned herein, such as implanting techniques, doping techniques, spin-on techniques, sputtering techniques, growth techniques, such as thermal growth and/or deposition techniques such as chemical vapor deposition (CVD), for example.

Moreover, “exemplary” is used herein to mean serving as an example, instance, illustration, etc., and not necessarily as advantageous. As used in this application, “or” is intended to mean an inclusive “or” rather than an exclusive “or”. In addition, “a” and “an” as used in this application and the appended claims are generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Also, at least one of A and B and/or the like generally means A or B or both A and B. Furthermore, to the extent that “includes”, “having”, “has”, “with”, or variants thereof are used, such terms are intended to be inclusive in a manner similar to the term “comprising”. Also, unless specified otherwise, “first,” “second,” or the like are not intended to imply a temporal aspect, a spatial aspect, an ordering, etc. Rather, such terms are merely used as identifiers, names, etc. for features, elements, items, etc. For example, a first spacer portion and a second spacer portion generally correspond to first spacer portion A and second spacer portion B or two different or two identical spacer portions or the same spacer portion.

Also, although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art based upon a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims. In particular regard to the various functions performed by the above described components (e.g., elements, resources, etc.), the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure. In addition, while a particular feature of the disclosure may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. 

What is claimed is:
 1. A semiconductor device, comprising: a metal gate stack comprising a high-k gate dielectric and a metal gate electrode over the high-k gate dielectric, wherein: the high-k gate dielectric has a tapered sidewall, the metal gate electrode has a tapered sidewall, a length of a top surface of the metal gate electrode is greater than a length of a bottom surface of the metal gate electrode, the tapered sidewall of the metal gate electrode extends from the bottom surface of the metal gate electrode to the top surface of the metal gate electrode, a length of a top surface of the high-k gate dielectric is no greater than the length of the bottom surface of the metal gate electrode, and a length of a bottom surface of the high-k gate dielectric is less than the length of the top surface of the high-k gate dielectric.
 2. The semiconductor device of claim 1, wherein the metal gate stack comprises a cap layer between the high-k gate dielectric and the metal gate electrode.
 3. The semiconductor device of claim 2, wherein the cap layer has a tapered sidewall.
 4. The semiconductor device of claim 3, wherein the tapered sidewall of the high-k gate dielectric, the tapered sidewall of the metal gate electrode, and the tapered sidewall of the cap layer have a common slope.
 5. The semiconductor device of claim 1, wherein the tapered sidewall of the high-k gate dielectric and the tapered sidewall of the metal gate electrode have a common slope.
 6. The semiconductor device of claim 1, wherein the metal gate stack comprises an interfacial layer below the high-k gate dielectric.
 7. The semiconductor device of claim 6, wherein the interfacial layer has a tapered sidewall.
 8. The semiconductor device of claim 7, wherein the tapered sidewall of the high-k gate dielectric, the tapered sidewall of the metal gate electrode, and the tapered sidewall of the interfacial layer have a common slope.
 9. The semiconductor device of claim 6, wherein the metal gate stack comprises a cap layer between the high-k gate dielectric and the metal gate electrode.
 10. The semiconductor device of claim 9, wherein: the interfacial layer has a tapered sidewall, and the cap layer has a tapered sidewall.
 11. The semiconductor device of claim 10, wherein the tapered sidewall of the high-k gate dielectric, the tapered sidewall of the metal gate electrode, the tapered sidewall of the interfacial layer, and the tapered sidewall of the cap layer have a common slope.
 12. The semiconductor device of claim 1, comprising: a sidewall spacer adjacent the metal gate stack, wherein a top surface of the sidewall spacer is co-planar with the top surface of the metal gate electrode.
 13. A semiconductor device, comprising: a metal gate stack comprising a high-k gate dielectric and a metal gate electrode over the high-k gate dielectric, wherein: the metal gate electrode comprises a top surface and a bottom surface, a length of the top surface of the metal gate electrode is greater than a length of the bottom surface of the metal gate electrode, the metal gate stack has a continuous slope from a bottom surface of the high-k gate dielectric to a top surface of the high-k gate dielectric and from the bottom surface of the metal gate electrode to the top surface of the metal gate electrode, and a length of the top surface of the high-k gate dielectric is greater than a length of the bottom surface of the high-k gate dielectric.
 14. The semiconductor device of claim 13, wherein: the metal gate stack comprises an interfacial layer below the high-k gate dielectric and in contact with a substrate, and a sidewall of the interfacial layer abuts a top surface of the substrate at a non-perpendicular angle.
 15. The semiconductor device of claim 13, wherein the metal gate stack comprises a cap layer between the high-k gate dielectric and the metal gate electrode.
 16. The semiconductor device of claim 15, wherein the cap layer is in contact with the high-k gate dielectric and the metal gate electrode.
 17. The semiconductor device of claim 13, comprising a sidewall spacer adjacent the metal gate stack and in contact with a substrate underlying the metal gate stack.
 18. The semiconductor device of claim 17, wherein an interior angle of the sidewall spacer, defined by a top surface of the substrate and a sidewall of the sidewall spacer that faces the metal gate stack, is less than 90 degrees.
 19. A semiconductor device, comprising: a metal gate stack comprising an interfacial layer, a high-k gate dielectric over the interfacial layer, and a metal gate electrode over the high-k gate dielectric, wherein: a length of a bottom surface of the high-k gate dielectric is greater than or equal to a length of a top surface of the interfacial layer, a length of a top surface of the high-k gate dielectric is greater than the length of the bottom surface of the high-k gate dielectric, a length of a bottom surface of the metal gate electrode is greater than or equal to the length of the top surface of the high-k gate dielectric, and the metal gate electrode has a tapered sidewall extending from a top surface of the metal gate electrode to the bottom surface of the metal gate electrode.
 20. The semiconductor device of claim 19, wherein: the length of the top surface of the interfacial layer is greater than a length of a bottom surface of the interfacial layer, and a length of the top surface of the metal gate electrode is greater than the length of the bottom surface of the metal gate electrode. 